CN109761865B

CN109761865B - Green preparation method of thiourea

Info

Publication number: CN109761865B
Application number: CN201910169713.3A
Authority: CN
Inventors: 程珍; 常忠臣; 马韵升; 张建林; 栾波
Original assignee: Shandong Efirm Biochemistry and Environmental Protection Co Ltd
Current assignee: Yifeng New Material Co.,Ltd.
Priority date: 2019-03-06
Filing date: 2019-03-06
Publication date: 2020-09-29
Anticipated expiration: 2039-03-06
Also published as: CN109761865A

Abstract

The invention belongs to the technical field of fine chemical engineering, relates to a thiourea synthesis technology, and particularly relates to a green preparation method of thiourea. The method takes cyanamide solution as a raw material, and hydrogen sulfide gas is introduced into the raw material under the condition of catalyst to react to prepare the cyanamide catalyst. The reaction temperature is 50-80 ℃, the mass concentration of the cyanamide aqueous solution is 15-90%, the catalyst is solid super acid, and the crystallization separation temperature of the thiourea product is-10-15 ℃. According to the thiourea synthesis method provided by the invention, the yield of thiourea can reach more than 90%, the purity can reach more than 99%, and the catalyst can be reused by filtration.

Description

Green preparation method of thiourea

Technical Field

The invention belongs to the technical field of fine chemical engineering, relates to a thiourea synthesis technology, and particularly relates to a green preparation method of thiourea.

Background

Thiourea is an important chemical raw material and is used as a raw material for synthesizing medicines such as sulfathiazole, methyl thiouracil, methionine and the like in medicine; rubber is industrially used as a vulcanization accelerator; mining and metallurgically as flotation agents. Thiourea is used as bleaching agent and coloring agent in textile industry, and is used as raw material for producing epoxy resin, dye and moulding powder. In the field of photographic materials, it can be used as developer and toner. It can also be used in the electroplating industry. Thiourea is also used in many fields such as diazo-sensitive paper, synthetic resin coating, anion exchange resin, germination accelerator, bactericide, etc.

Regarding the synthesis of thiourea, most of the documents report that the thiourea solution is obtained by absorbing hydrogen sulfide with lime nitrogen aqueous solution under a slight negative pressure to generate calcium hydrosulfide, and then reacting with lime nitrogen. The synthesis method has the advantages of long reaction time, more side reactions, lower yield and waste residue generation. And the yield of other synthetic methods is not more than 70 percent, so that a high-yield thiourea green synthetic process needs to be developed.

Disclosure of Invention

Aiming at the defects of the technology, the invention provides a green preparation method of thiourea, which takes cyanamide aqueous solution and hydrogen sulfide as raw materials to synthesize the thiourea under the action of a catalyst. The whole process has no pollution to the environment, low cost, high yield of thiourea up to more than 90 percent, suitability for industrial scale thiourea generation, no pollution in the whole process, low cost, high product yield and good quality.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a green preparation method of thiourea comprises the following specific technical scheme:

in a high-pressure kettle, cyanamide aqueous solution is used as a raw material, excessive hydrogen sulfide gas is introduced under the action of a catalyst, the solid catalyst obtained after the reaction is finished is filtered and can be recycled, and the filtrate is cooled, crystallized and separated to obtain a thiourea product.

The catalyst is SO₄ ^2-/M_xO_yType solid superacid, in particular SO₄ ^2-/TiO₂Or SO₄ ^2-/ZrO₂Or SO₄ ^2-/Fe₂O₃And the like.

The amount of the hydrogen sulfide introduced is preferably 1.01 to 1.1 times that of the cyanamide.

The addition amount of the catalyst is 1 to 10 percent, preferably 5 percent of the mass of the cyanamide.

The mass concentration of the cyanamide aqueous solution is 15-90%, preferably 50%.

The reaction temperature is as follows: 50 ℃ to 80 ℃, preferably 65 ℃.

The reaction time is 1-3 hours, preferably 2 hours.

In the reaction process, the flow of the introduced hydrogen sulfide gas is controlled, and the pressure of the reaction kettle is controlled within 0.4 MPa.

The temperature reduction and crystallization temperature is as follows: -10 ℃ to 15 ℃, preferably 5 ℃.

Compared with the prior art, the invention has the beneficial effects that:

the solid super acid is used as a catalyst, the cyanamide is firstly activated in an acid center of the solid super acid and then reacts with hydrogen sulfide to generate thiourea, the reaction yield is higher, and different from the alkali catalysis, the yield of the thiourea is up to more than 90 percent, compared with the prior art (65 percent), the yield is obviously improved, the product thiourea is separated by adopting a freezing crystallization method, the product purity is up to more than 99 percent after recrystallization, and the solid catalyst can be reused by filtering. The solid super acid in the invention is prepared by adopting the prior art.

Detailed Description

The following further description of the present invention is provided in connection with specific embodiments to enable those skilled in the art to further understand the present invention, and not to limit the present invention, and all techniques based on the principles described herein are within the scope of the present invention.

The raw materials used in the invention are as follows: 30% aqueous cyanamide solution, 50% aqueous cyanamide solution: a commercially available product; hydrogen sulfide: commercial product, content 99%; solid super acidic SO₄ ^2-/TiO₂，SO₄ ^2-/ZrO₂，SO₄ ^2-/Fe₂O₃: the prior conventional technology (see the literature: Lvchengfei, SO 4- (2-)/M _ xO _ y type solid superacid preparation and the research of catalytic synthesis of isoamyl acetate [ D ]]University of Dalian traffic, 2008) with a purity of 99%.

Example 1

Weighing solid super acidic SO₄ ^2-/TiO₂12.5g of the mixture is added into 500g of cyanamide aqueous solution with the mass fraction of 50 percent, the stirring speed is 150r/min, the temperature is 65 ℃, the introduction flow of the hydrogen sulfide is 1.2L/min, the reaction is stopped after the hydrogen sulfide is continuously introduced for 2 hours, and the pressure in the kettle is controlled within 0.4MPa in the reaction process. Filtering, recovering the solid catalyst, freezing and crystallizing the filtrate in a crystallizer at 5 ℃, filtering and separating the product, drying, and analyzing by adopting a national standard HG/T3266 and 2002 method.

The results of using the catalyst 5 times in succession under the same reaction conditions are shown in table 1.

Table 1:

example 2

Weighing solid super acidic SO₄ ^2-/TiO₂15g of the mixture is added into 500g of cyanamide aqueous solution with the mass fraction of 30 percent, and the mixture is stirredThe reaction speed is 150r/min, the reaction temperature is 50 ℃, the introduction flow of the hydrogen sulfide is 1.4L/min, the reaction is stopped after the hydrogen sulfide is continuously introduced for 1 hour, and the pressure in the kettle is controlled within 0.4MPa in the reaction process. Filtering, recovering the solid catalyst, freezing and crystallizing the filtrate in a crystallizer at 15 ℃, filtering and separating the product, drying, and analyzing by adopting a national standard HG/T3266 and 2002 method.

The reaction temperature was changed (65 ℃ C., 80 ℃ C.), and the other conditions were not changed, and the results are shown in Table 2.

Table 2:

example 3

Weighing solid super acidic SO₄ ^2-/ZrO₂Adding 7.5g of the mixture into 500g of cyanamide aqueous solution with the mass fraction of 50%, stirring at the rotating speed of 150r/min and the temperature of 80 ℃, introducing hydrogen sulfide at the flow rate of 0.8L/min, stopping the reaction after continuously introducing the hydrogen sulfide for 3 hours, and controlling the pressure in the kettle within 0.4MPa in the reaction process. Filtering, recovering the solid catalyst, freezing and crystallizing the filtrate in a crystallizer at 5 ℃, filtering and separating the product, drying, and analyzing by adopting a national standard HG/T3266 and 2002 method. The results are shown in Table 3.

Table 3:

example 4

Weighing solid super acidic SO₄ ^2-/Fe₂O₃12.5g of the mixture is added into 500g of cyanamide aqueous solution with the mass fraction of 50 percent, the stirring speed is 150r/min, the temperature is 65 ℃, the introduction flow of the hydrogen sulfide is 1.2L/min, the reaction is stopped after the hydrogen sulfide is continuously introduced for 2 hours, and the pressure in the kettle is controlled within 0.4MPa in the reaction process. Filtering, recovering the solid catalyst, freezing and crystallizing the filtrate in a crystallizer at-10 ℃, filtering and separating the product, drying, and analyzing by using a national standard HG/T3266-2002 method, wherein the results are shown in Table 4.

Table 4:

comparative example

According to the method in the patent publication document with the patent application number of 2011101041293 and the name of thiourea clean production method, 1.5L of industrial ammonia water (22% -25%) is used as a catalyst for reaction, hydrogen sulfide is introduced, the flow rate is 1.2L/min, the stirring speed is 150r/min, 500g of cyanamide aqueous solution with the mass fraction of 50% is added at the flow rate of 10mL/min after 0.5 hour of hydrogen sulfide is introduced, the reaction temperature is 65 ℃, the reaction is stopped after hydrogen sulfide is continuously introduced for 40 minutes after the cyanamide is completely added, and the total reaction time is 2 hours. The mother liquor is frozen and crystallized at 5 ℃ in a crystallizer, and the product is analyzed by adopting a national standard HG/T3266-2002 method after being filtered, separated and dried.

Example 1 was compared to the results of the invention, as shown in table 5:

TABLE 5

Compared with the prior art, the method disclosed by the invention has the advantages that on the premise of ensuring and even improving the purity of the thiourea product, the yield of the thiourea is greatly improved, the reaction operation can be simplified, the catalyst can be repeatedly used for many times, the catalytic effect is ensured, the whole reaction process is free from environmental pollution, the cost is low, the yield of the thiourea is up to more than 90%, and the method is suitable for industrial-scale production of the thiourea.

Claims

1. A green preparation method of thiourea is characterized in that: in a high-pressure kettle, taking a cyanamide aqueous solution as a raw material, introducing excessive hydrogen sulfide gas under the action of a catalyst, filtering after the reaction is finished, and cooling, crystallizing and separating filtrate to obtain a thiourea product; the catalyst is SO₄ ^2-/M_xO_ySolid super acid.

2. A process for the green preparation of thiourea according to claim 1, characterized in that: SO (SO)₄ ^2-/M_xO_yThe type solid super acid is specifically SO₄ ^2-/TiO₂Or SO₄ ^2-/ZrO₂Or SO₄ ^2-/Fe₂O₃。

3. A process for the green preparation of thiourea according to claim 1, characterized in that: the addition amount of the catalyst is 1-10% of the mass of the cyanamide.

4. A green process for the preparation of thiourea according to claim 3, characterized in that: the addition amount of the catalyst is 5 percent of the mass of the cyanamide.

5. A green process for the preparation of thiourea according to claim 1, wherein: the amount of the hydrogen sulfide introduced is 1.01-1.1 times of that of the cyanamide.

6. A green process for the preparation of thiourea according to claim 1, wherein: the mass concentration of the cyanamide aqueous solution is 15-90%.

7. A green process for the preparation of thiourea according to claim 1, wherein: the reaction temperature is as follows: 50-80 ℃.

8. A green process for the preparation of thiourea according to claim 1, wherein: the reaction time is 1-3 hours.

9. A process for the green preparation of thiourea according to claim 1, characterized in that: the temperature reduction and crystallization temperature is as follows: -10 ℃ to 15 ℃.